Electric motor pole position sensing method, pole position sensing apparatus, and electric motor control apparatus using the same

ABSTRACT

It is an object of the invention to provide a method which can detect a magnetic pole position easily and surely by using high-frequency currents such as harmonics of an inverter output and carrier frequency components. The invention provides a method of detecting a magnetic pole position of a motor and an apparatus for detecting a magnetic pole position in which, although high-frequency currents of carrier frequency components or the like are used, a special current detecting circuit is not required, and synchronization between the current detection timing and the position calculation can be easily attained, and also to provide an apparatus for controlling a motor using the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on a Japanese patent application(JP-A-2001-238060) filed Aug. 6, 2001, and the contents of the patentapplication are incorporated herein by reference.

1. Field of the Invention

The present invention relates to an apparatus for controlling a motorwhich accurately estimates a magnetic pole position at a very low speedincluding zero speed, and which controls the torque and the speed on thebasis of the estimated magnetic pole position.

2. Description of the Related Art

As a conventional method of estimating a magnetic pole position, widelyused is a method in which an induced voltage that is proportional to amotor speed is calculated from a motor input voltage and a current, suchas that reported in “Adaptive Current Control Method for Brushless DCmotor with Function of Parameter Identification” IEEJ Transactions onIndustry Applications, Vol. 108 No. 12, 1988. Also known is “Zero SpeedTorque Control of Sensorless Salient-Pole Synchronous Motor” 1996National Convention of IEEJ Industry Applications Society No. 170. Inthis technique, an AC signal is superimposed on a voltage command value,and a detected current is FFT analyzed to detect the rotational speed ofa motor and a magnetic pole position. However, a method, which estimatesthe speed and position of a rotor on the basis of an induced voltage ofa motor, operates with sufficient accuracy in a high speed region, butcannot perform correct estimation at a very low speed from which littleinformation of the induced voltage is obtained.

Therefore, several methods have been proposed in which an AC signal thathas no relation to a driving frequency, and that is used for sensing isinjected into a motor, and a rotor position is estimated fromrelationships between the voltage and the current. However, a specialsignal generator is necessary in order to inject such a sensing signal,thereby causing a problem in that the control is complicated. Othermethods in which a special sensing signal is not injected and a magneticpole position is detected by using harmonics of an inverter output orcurrents of carrier frequency components are reported in “PositionSensorless IPM Motor Drive System Using Position Estimation Method Basedon Saliency” IEEJ Transactions on Industry Applications, Vol. 118 No. 5,1998, and “Carrier Frequency Component Method for Position SensorlessControl of IPM Motor in Lower Speed Range” IEEJ Transactions on IndustryApplications, Vol. 120 No. 2, 2000.

The former method is characterized in that an inductance is calculatedfrom high-frequency currents generated by output voltage harmonics of aPWM inverter, and the position is detected on the basis of theinductance. The latter method is characterized in that a phasedifference of 120 deg. is produced between PWM inverter carrier signalsof two of three or U-, V-, and W-phases to generate voltages andcurrents of carrier frequency components other than the drivingfrequency, and the position is detected by using only the carrierfrequency component currents based on the assumption that a voltageduring the carrier period is constant.

The methods which detect a magnetic pole position by using harmonics ofan inverter output or high-frequency currents of carrier frequencycomponents have an advantage that a special sensing signal generator isnot necessary. However, the methods require plural current detectionsduring the carrier period. Therefore, a special current detectingcircuit is required, and synchronization between the current detectiontiming and the position calculation is complicated. Consequently, it isdifficult to practically use such methods.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a method of detecting amagnetic pole position of a motor and an apparatus for detecting amagnetic pole position in which, although high-frequency currents ofcarrier frequency components or the like are used, a special currentdetecting circuit is not required, and synchronization between thecurrent detection timing and the position calculation can be easilyattained, and also to provide an apparatus for controlling a motor usingthe same.

In order to attain the object, the first aspect of the inventionprovides a method of detecting a magnetic pole position of a motorhaving electric saliency wherein an arbitrary high frequency other thanan output frequency of a voltage source PWM inverter is generated ininput voltages or currents of a motor by means for producing anarbitrary phase difference between respective two phases such as UV, VW,or WU in the inverter, the voltages or currents are converted to atwo-phase stationary coordinate system in which U-phase of three phasesof the motor is α-axis and an axis intersecting the axis at 90 deg. isβ-axis, a current of the arbitrary high-frequency component is detectedin each of the α- and β-axes, the voltages or currents are converted toa two-phase stationary coordinate system in which a phase is similarlyshifted by 45 deg. from the two-phase stationary coordinate system, orin which an axis that is shifted by 45 deg. from the α-axis is α′-axisand an axis intersecting the axis at 90 deg. is β′-axis, a current ofthe arbitrary high-frequency component is detected in each of the α′-and β′-axes, and a magnetic pole position of the motor is detected byusing the high-frequency current components that are detectedrespectively in the four axes.

The second aspect of the invention is characterized in that, in themethod of detecting a magnetic pole position of a motor according to thefirst aspect, the magnetic pole position of the motor is detected byusing an output which is obtained by extracting peak currents from thehigh-frequency current components that are detected respectively in thefour axes, and then passing the peak currents through a low-pass filter.

The third aspect of the invention provides an apparatus for detecting amagnetic pole position for a controlling apparatus for driving a motorby a voltage source PWM inverter wherein the apparatus comprises: meansfor producing an arbitrary phase difference in PWM carrier signalsbetween respective two phases such as UV, VW, or WU of three or U-, V-,and W-phases; means for extracting high-frequency voltages andhigh-frequency currents that are generated by it, from detected voltagesor a command voltage and detected currents; and means for detecting amagnetic pole position by using the extracted high-frequency voltagesand currents.

The fourth aspect of the invention provides an apparatus for detecting amagnetic pole position for a controlling apparatus for driving a motorby a voltage source PWM inverter wherein the apparatus comprises: meansfor producing an arbitrary phase difference in PWM carrier signalsbetween respective two phases such as UV, VW, or WU of three or U-, V-,and W-phases; means for extracting only high-frequency currents that aregenerated by it; and means for detecting a magnetic pole position byusing the extracted high-frequency currents.

The fifth aspect of the invention is characterized in that, in theapparatus for detecting a magnetic pole position of a motor according tothe fourth aspect, the method of detecting a magnetic pole positionaccording to the first aspect is used as the means for detecting amagnetic pole position.

The sixth aspect of the invention is characterized in that, in theapparatus for detecting a magnetic pole position of a motor according tothe fourth aspect, the method of detecting a magnetic pole positionaccording to the second aspect is used as the means for detecting amagnetic pole position.

The seventh aspect of the invention is characterized in that thearbitrary phase difference is 120 deg., and the arbitrary high frequencyis an inverter carrier frequency.

The eighth aspect of the invention is characterized in that thearbitrary phase difference is 120 deg., and the arbitrary high frequencyis an inverter carrier frequency.

The ninth aspect of the invention is characterized in that the arbitraryphase difference is 120 deg., and the arbitrary high frequency is aninverter carrier frequency.

The tenth aspect of the invention is characterized in that an apparatuscomprises a current controlling apparatus which splits a detectedcurrent into a pole direction component and a torque component by usingthe position detected by the apparatus for detecting a magnetic poleposition according to any one of the third and the fourth aspects, whichfeedbacks the components to compare the components with current commandvalues for the pole direction component and the torque component, andwhich implements a current control so that deviations in the comparisonsbecome zero.

The eleventh aspect of the invention is characterized in that theapparatus comprises a speed detecting apparatus which detects a speed byusing the position detected by the apparatus for detecting a magneticpole position according to any one of the third and the fourth aspects.

The twelfth aspect of the invention is characterized in that theapparatus comprises a speed controlling apparatus which compares thespeed detected on the basis of the speed detecting apparatus of theapparatus for controlling a motor according to the eleventh aspect, witha command speed, which implements a speed control so that a deviation inthe comparison becomes zero, and which outputs a torque command value ora current command value corresponding to a torque command.

The thirteenth aspect of the invention is characterized in that theapparatus comprises a position controlling apparatus which compares themagnetic pole position detected on the basis of the apparatus fordetecting a magnetic pole position according to any one of the third andthe fourth aspects, with a command position, which implements a positioncontrol so that a deviation in the comparison becomes zero, and whichoutputs a speed command value.

The fourteenth aspect of the invention is characterized in that theapparatus comprises a torque controlling apparatus having: the apparatusfor detecting a magnetic pole position according to the ninth aspect;and the current controlling apparatus according to the tenth aspect.

The fifteenth aspect of the invention is characterized in that theapparatus comprises a speed controlling apparatus having: the apparatusfor detecting a magnetic pole position according to the ninth aspect;the current controlling apparatus according to the tenth aspect; thespeed detecting apparatus according to the eleventh aspect, and thespeed controlling apparatus according to the twelfth aspect.

The sixteenth aspect of the invention is characterized in that theapparatus comprises a position controlling apparatus having: theapparatus for detecting a magnetic pole position according to the ninthaspect; the current controlling apparatus according to the tenth aspect;the speed detecting apparatus according to the eleventh aspect, thespeed controlling apparatus according to the twelfth aspect; and theposition controlling apparatus according to the thirteenth aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a) to 1(c) show the illustration views of the principle of themethod of detecting a magnetic pole position of a motor according to theinvention;

FIG. 2 is a control block diagram of an apparatus for detecting amagnetic pole position of a motor shown in FIG. 1;

FIG. 3 is a block diagram of a PWM controller shown in FIG. 2; and

FIG. 4 is a diagram showing the configuration of a pole positiondetector shown in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

First, the invention is based on a method of detecting a magnetic poleposition by using a current of a carrier frequency component, and thebasic principle of the magnetic pole position detection will bedescribed. In a vector controlling apparatus for a synchronous motorwhich is driven by a voltage source PWM inverter, an arbitrary phasedifference is produced between PWM carrier signals of respective twophases such as UV, VW, or WU of three or U-, V-, and W-phases, therebygenerating high-frequency voltages and high-frequency currents that aredifferent from a driving frequency. Namely, the frequency band ofgenerated high-frequency components can be adjusted to a frequencydifferent from the driving frequency by arbitrarily giving thefrequencies of the PWM carriers and the phase difference of thecarriers. When the phase difference is 120 deg., for example, voltageand current components the frequencies of which are equal to the carrierfrequency largely appear. In this case, the high-frequency voltages canbe expressed by the following expression:

$\begin{bmatrix}u_{uh} \\u_{vh} \\u_{wh}\end{bmatrix} = \begin{bmatrix}{V\;{\sin\left( {\omega_{h}t} \right)}} \\{V\;{\sin\left( {{\omega_{h}t} - {2\;{\pi/3}}} \right)}} \\{V\;{\sin\left( {{\omega_{h}t} + {2\;{\pi/3}}} \right)}}\end{bmatrix}$where uuh, uvh, and uwh indicate high-frequency voltages of the U-, V-,and W-phases, respectively, V indicates the amplitude of ahigh-frequency voltage, and ω_(h) indicates a carrier angular frequency.

Furthermore, relationships between the high-frequency voltages and thehigh-frequency currents are expressed by following expression (1):

$\begin{matrix}{\begin{bmatrix}u_{uh} \\u_{vh} \\u_{wh}\end{bmatrix} = {\begin{bmatrix}L_{uu} & L_{uv} & L_{vw} \\L_{vu} & L_{vv} & L_{vw} \\L_{wu} & L_{wv} & L_{ww}\end{bmatrix}{\frac{\mathbb{d}\;}{\mathbb{d}t}\begin{bmatrix}i_{uh} \\i_{vh} \\i_{wh}\end{bmatrix}}}} & (1)\end{matrix}$where iuh, ivh, and iwh indicate high-frequency currents of the U-, V-,and W-phases, respectively, L indicates an inductance, Luu, Lvv, and Lwwindicate self inductances of the U-, V-, and W-phases, respectively, andthe others indicate phase-to-phase inductances. A motor in which apermanent magnet is used in a rotor has electric salient poles (thismeans that the d-axis inductance and the q-axis inductance are differentfrom each other). Therefore, the inductances contain information of amagnetic pole position.L _(uv) =−L _(g0)/2+L _(g2) cos (2θ−2π/3)L _(vw) =−L _(g0)/2+L _(g2) cos (2θ)L _(uw) =−L _(g0)/2+L _(g2) cos (2θ+2π/3)L _(uu) =L _(s) +L _(g0) +L _(g2) cos (2θ)L _(vv) =L _(s) +L _(g0) +L _(g2) cos (2θ+2π/3)L _(ww) =L _(s) +L _(g0) +L _(g2) cos (2θ−2π/3)where Lg0 indicates the magnetizing inductance in the air gap flux, Lsindicates the leakage inductance of a stator, and Lg2 indicates aninductance the degree of which depends on the angle.

When expression (1) is converted to a stator-based stationary coordinatesystem, following expression (2) is obtained:

$\begin{matrix}{\begin{bmatrix}u_{\alpha\; h} \\u_{\beta\; h}\end{bmatrix} = {\begin{bmatrix}{L_{0} + {L_{1}\cos\mspace{11mu}\left( {2\theta} \right)}} & {L_{1}{\sin\left( {2\theta} \right)}} \\{L_{1}{\sin\left( {2\theta} \right)}} & {L_{0} - {L_{1}{\cos\left( {2\theta} \right)}}}\end{bmatrix}{\frac{\mathbb{d}\;}{\mathbb{d}t}\begin{bmatrix}i_{\alpha\; h} \\i_{\beta\; h}\end{bmatrix}}}} & (2)\end{matrix}$where L0=Ls+3Lg0/2, and L1=3Lg2/2.

From expression (2), magnetic pole position information sin (2θ) and cos(2θ) are derived:

$\begin{matrix}{\begin{bmatrix}{\cos\left( {2\;\theta} \right)} \\{\sin\left( {2\;\theta} \right)}\end{bmatrix} = {\frac{1}{L_{1}\left\lbrack {\left( {\frac{\mathbb{d}}{\mathbb{d}t}i_{\alpha h}} \right)^{2} + \left( {\frac{\mathbb{d}}{\mathbb{d}t}i_{\beta\; h}} \right)^{2}} \right\rbrack} \times \mspace{149mu}\begin{bmatrix}{{u_{\alpha\; h}\frac{\mathbb{d}}{\mathbb{d}t}i_{\alpha\; h}} - {u_{\beta\; h}\frac{\mathbb{d}}{\mathbb{d}t}i_{\beta\; h}} - {L_{0}\left\{ {\left( {\frac{\mathbb{d}}{\mathbb{d}t}i_{\alpha\; h}} \right)^{2} - \left( {\frac{\mathbb{d}}{\mathbb{d}t}i_{\beta\; h}} \right)^{2}} \right\}}} \\{{u_{\alpha\; h}\frac{\mathbb{d}}{\mathbb{d}t}i_{\beta\; h}} + {u_{\beta\; h}\frac{\mathbb{d}}{\mathbb{d}t}i_{\alpha\; h}} - {2{L_{0}\left( {\frac{\mathbb{d}}{\mathbb{d}t}i_{\alpha\; h}\frac{\mathbb{d}}{\mathbb{d}t}i_{\beta\; h}} \right)}}}\end{bmatrix}}} & (3)\end{matrix}$

In this way, the magnetic pole position can be estimated by using thehigh-frequency voltages and the high-frequency currents.

When the estimation mechanism is synchronized with the carrier frequencyand the current is sampled at a point where a high-frequency currentiβ_(h) reaches a peak, iα_(h) which is separated in phase by 90 deg. issubstantially zero. Therefore, expression (3) can be expressed in asimpler manner as following expression (4):

$\begin{matrix}{\begin{bmatrix}{\cos\left( {2\theta} \right)} \\{\sin\left( {2\theta} \right)}\end{bmatrix} = {{\frac{1}{{L_{1}\left( {\frac{\mathbb{d}\;}{\mathbb{d}t}i_{\beta\; h}} \right)}^{2}}\begin{bmatrix}{{{- u_{\beta\; h}}\frac{\mathbb{d}\;}{\mathbb{d}t}i_{\beta\; h}} + {L_{0}\left( {\frac{\mathbb{d}\;}{\mathbb{d}t}i_{\beta\; h}} \right)}^{2}} \\{u_{\alpha\; h}\frac{\mathbb{d}\;}{\mathbb{d}t}i_{\beta\; h}}\end{bmatrix}} = \begin{bmatrix}\frac{- u_{\beta\; h}}{\left( {L_{1}\frac{\mathbb{d}\;}{\mathbb{d}t}i_{\beta\; h}} \right) + L_{0}} \\\frac{u_{\alpha\; h}\;}{\left( {L_{1}\frac{\mathbb{d}\;}{\mathbb{d}t}i_{\beta\; h}} \right)}\end{bmatrix}}} & (4)\end{matrix}$

From expressions (3) and (4) above, cos (2θ) and sin (2θ) are obtained,the value of the angle 2θ is obtained on the basis of the informationvalues from a table of trigonometric functions which is previouslyprepared in a calculator, and the value is divided by 2, whereby themagnetic pole position θ (hereinafter) can be detected. In thecalculations of expressions (3) and (4), current differentiation valuesare used. At a high speed, the currents are rapidly changed, and hencethe magnetic pole position is vibratory. From expression (2), therefore,current differentiation values are obtained as shown in expression (5).When both sides are integrated, expression (6) is obtained.

$\begin{matrix}{{\frac{\mathbb{d}}{\mathbb{d}t}\begin{bmatrix}i_{\alpha\; h} \\i_{\beta\; h}\end{bmatrix}} = {{\frac{1}{L_{0}^{2} - L_{1}^{2}}\begin{bmatrix}{L_{0} - {L_{1}{\cos\left( {2\;\theta} \right)}}} & {{- L_{1}}{\sin\left( {2\;\theta} \right)}} \\{{- L_{1}}{\sin\left( {2\;\theta} \right)}} & {L_{0} + {L_{1}{\cos\left( {2\;\theta} \right)}}}\end{bmatrix}}\begin{bmatrix}u_{\alpha\; h} \\u_{\beta\; h}\end{bmatrix}}} & (5) \\{\begin{bmatrix}i_{\alpha\; h} \\i_{\beta\; h}\end{bmatrix} = {{\frac{1}{L_{0}^{2} - L_{1}^{2}}\begin{bmatrix}{L_{0} - {L_{1}{\cos\left( {2\;\theta} \right)}}} & {{- L_{1}}{\sin\left( {2\;\theta} \right)}} \\{{- L_{1}}{\sin\left( {2\;\theta} \right)}} & {L_{0} + {L_{1}{\cos\left( {2\;\theta} \right)}}}\end{bmatrix}}\begin{bmatrix}{\int{u_{\alpha\; h}{\mathbb{d}t}}} \\{\int{u_{\beta\; h}{\mathbb{d}t}}}\end{bmatrix}}} & (6)\end{matrix}$

From expression (6), the magnetic pole position information sin (2θ) andcos (2θ) are derived:

$\begin{matrix}{\begin{bmatrix}{\cos\left( {2\;\theta} \right)} \\{\sin\left( {2\;\theta} \right)}\end{bmatrix} = {\frac{1}{L_{1}\left\{ {\left( {\int{u_{\alpha\; h}{\mathbb{d}t}}} \right)^{2} + \left( {\int{u_{\beta\; h}{\mathbb{d}t}}} \right)^{2}} \right\}} \times \mspace{59mu}\begin{bmatrix}\begin{matrix}{{L_{0}\left\{ {\left( {\int{u_{\alpha\; h}{\mathbb{d}t}}} \right)^{2} - \left( {\int{u_{\beta\; h}{\mathbb{d}t}}} \right)^{2}} \right\}} -} \\{\left( {L_{0}^{2} - L_{1}^{2}} \right)\left( {{i_{\alpha\; h}{\int{u_{\alpha\; h}{\mathbb{d}t}}}} - {i_{\beta\; h}{\int{u_{\beta\; h}{\mathbb{d}t}}}}} \right)}\end{matrix} \\{{2L_{0}{\int{u_{\alpha\; h}{\mathbb{d}t}{\int{u_{\beta\; h}{\mathbb{d}t}}}}}} - {\left( {L_{0}^{2} - L_{1}^{2}} \right)\left( {{i_{\alpha\; h}{\int{u_{\beta\; h}{\mathbb{d}t}}}} + {i_{\beta\; h}{\int{u_{\alpha\; h}{\mathbb{d}t}}}}} \right)}}\end{bmatrix}}} & (7)\end{matrix}$In the case where the carrier period is synchronized with the voltagesampling period, the voltage integration value is dealt as a fixed valueas in the following expression. In an inverter of a usual controlvoltage source, the voltage integration value is a fixed value duringthe carrier period.∫u _(αh) dt=u _(αh) Δt, ∫u _(βh) dt=u _(βh) ΔtΔt: sampling time

When uαh is a peak voltage, uβh=0. At this timing, therefore, cos (2θ)is calculated from expression (7) as follow:

${\cos\left( {2\theta} \right)} = {\frac{L_{0}}{L_{1}} - {\frac{\left( {L_{0}^{2} - L_{0}^{2}} \right)}{L_{1}} \cdot \frac{\left. i_{\alpha\; h} \right|_{\theta = {0{^\circ}}}}{\left. u_{\alpha\; h} \middle| {}_{\theta = {0{^\circ}}}{{\cdot \Delta}\; t} \right.}}}$

When uβh is a peak voltage, uαh=0. At this timing, therefore, cos (2θ)is calculated from expression (7) as follow:

$\begin{matrix}{{\cos\left( {2\;\theta} \right)} = {{- \frac{L_{0}}{L_{1}}} + {\frac{\left( {L_{0}^{2} - L_{1}^{2}} \right)}{L_{1}} \cdot \frac{\left. i_{\beta\; h} \right|_{\theta = {90{^\circ}}}}{u_{\beta\; h}❘_{\theta = {90{^\circ}}}{{\cdot \Delta}\; t}}}}} & (8)\end{matrix}$

At the point where θ is advanced by 45 deg. from the point of uαh=0,uαh=uβh. At this timing, therefore, sin (2θ) is calculated fromexpression (7) as follow:

$\begin{matrix}{{\sin\left( {2\;\theta} \right)} = {\frac{L_{0}}{L_{1}} - {\frac{\left( {L_{0}^{2} - L_{1}^{2}} \right)}{L_{1}} \cdot \frac{\left( {i_{\alpha\; h} + i_{\beta\; h}} \right)❘_{\theta = {45{^\circ}}}}{\left( {u_{\alpha\; h} + u_{\beta\; h}} \right)❘_{\theta = {45{^\circ}}}{{\cdot \Delta}\; t}}}}} & (9)\end{matrix}$

At the point where θ is advanced by 135 deg. from the point of uαh=0,uαh=−uβh. At this timing, therefore, sin (2θ) is calculated fromexpression (7) as follow:

$\begin{matrix}{{\sin\;\left( {2\theta} \right)} = {{- \frac{L_{0}}{L_{1}}} + {\frac{\left( {L_{0}^{2} - L_{0}^{2}} \right)}{L_{1}} \cdot \frac{\left. \left( {i_{\alpha\; h} - i_{\beta\; h}} \right) \right|_{\theta = {135{^\circ}}}}{\left. \left( {u_{\alpha\; h} + u_{\beta\; h}} \right) \middle| {}_{\theta = {135{^\circ}}}{{\cdot \Delta}\; t} \right.}}}} & (10)\end{matrix}$As a result, it is possible to detect the position of the magnetic pole.In order to realize this method of detecting a magnetic pole position,however, the high-frequency currents at the timings of uαh=0 and uαh=uβhmust be correctly detected, and hence this technique is hardly performedin a practical use. In the invention, therefore, the followingmodification is applied to solve the problem.

FIG. 1 shows the principle of the detection of a magnetic pole positionaccording to the invention. In the figures, the reference numeral 1denotes a speed controller, 2 denotes a q-axis current controller, 3denotes a noninterference controller, 4 denotes a d-axis currentcontroller, 5 denotes a voltage amplitude and phase calculator, 6denotes a PWM controller, 6-1 denotes a three-phase voltage commandcalculator, 6-2 denotes a comparator, 6-3 denotes a phase shifter, 6-4denotes a carrier signal generator, 7 denotes an inverter main circuit,8 denotes an AC motor, 9 denotes a stationary coordinate converter, 10denotes a rotating coordinate converter, 11 denotes a band-pass filter,12 denotes a pole position detector, 13 denotes a speed calculator, 14denotes a coordinate converter, 15 denotes an absolute value calculator,16 denotes a low-pass filter, and 17 denotes a pole position calculator.

When, as shown in FIG. 1( a), a two-phase stationary coordinate systemin which the U-phase of the three phases of the motor is α-axis and anaxis intersecting the axis at 90 deg. is β-axis is set, and a two-phasestationary coordinate system in which an axis that is shifted by 45 deg.from the α-axis is α′-axis and an axis intersecting the axis at 90 deg.is β′-axis is set, inductances in the axes are indicated as expressions(11) to (14) below.

The inductance in the α-axis is:L _(α)(θ)=L ₀ −L ₁cos (2θ)  (11)

In the expressions, θ, θ′, θ″, and θ″′ are variables of the phase inwhich the respective α-, β-, α′-, and β′-axes are zero deg.

This state is shown in FIG. 1( b) indicating that the magnetic poleposition coincides with the α-axis.

Assuming that the phase is advanced so that the magnetic pole positionis shifted from the α-axis by Δθ FIG. 1( c), the inductance in theα-axis is:L _(α) =L ₀ −L ₁ cos (−2Δθ)=L ₀ −L ₁ cos (2Δθ),  (15)the inductance in the β-axis is:L _(β) =L ₀ +L ₁ cos (−2Δθ)=L ₀ +L ₁ cos (2Δθ),  (16)the inductance in the α′-axis is:L _(α′) =L ₀ +L ₁ sin (−2Δθ)=L ₀ −L ₁ sin (2Δθ),  (17)the inductance in the β′-axis is:L _(β) =L ₀ −L ₁ sin (−2Δθ)=L ₀ +L ₁ sin (2Δθ),  (18)

Expression (16) is subtracted from expression (15) to extract only themagnetic pole position information as follow:L _(α) −L _(β) =−L ₁ cos (2Δθ)  (19)

Similarly, expression (18) is subtracted from expression (17) to obtainthe following:L _(α′) −L _(β′) =−L ₁ sin (2Δθ)  (20)

The magnetic pole position can be detected by following expression (21):

$\begin{matrix}{{\tan\left( {2\;\Delta\;\theta} \right)} = \frac{L_{\alpha^{\prime}} - L_{\beta^{\prime}}}{L_{\alpha} - L_{\beta}}} & (21)\end{matrix}$

Hereinafter, the calculations of the inductances will be specificallydescribed.

In expressions (8) to (10), θ=Δθ is set. When the resulting expressionsare substituted to expressions (15) to (18), the following are obtained:

$\begin{matrix}{L_{\alpha} = {\left( {L_{0}^{2} - L_{1}^{2}} \right) \cdot \frac{i_{\alpha\; h}}{{u_{\alpha\; h} \cdot \Delta}\; t}}} & (22) \\{L_{\beta} = {{- \left( {L_{0}^{2} - L_{1}^{2}} \right)} \cdot \frac{i_{\beta\; h}}{{u_{\beta\; h} \cdot \Delta}\; t}}} & (23) \\{L_{\alpha^{\prime}} = {\left( {L_{0}^{2} - L_{1}^{2}} \right) \cdot \frac{i_{\alpha^{\prime}\; h}}{{u_{\alpha^{\prime}\; h} \cdot \Delta}\; t}}} & (24) \\{L_{\beta^{\prime}} = {{- \left( {L_{0}^{2} - L_{1}^{2}} \right)} \cdot \frac{i_{\beta^{\prime}\; h}}{{u_{\beta^{\prime}\; h} \cdot \Delta}\; t}}} & (25)\end{matrix}$where

-   -   iα′_(h)=(iα_(h)+iβ_(h))|θ_(=45°),    -   iβ′_(h)=(iα_(h)+iβ_(h))|θ_(=135°),    -   uα′_(h)=(uα_(h)+uβ_(h))|θ_(=45°), and    -   uβ′_(h)=(uα_(h)+uβ_(h))|θ_(=135°).

When the voltage in the carrier period is dealt as a fixed value, theinductances can be calculated by using only the carrier frequencycomponent currents which are converted to the coordinates, respectively.Namely, the followings are obtained:L _(α) ∝|i _(αh)|_(αv)  (26)L _(β) ∝|i _(βh)|_(αv)  (27)L _(α′) ∝|i _(α′h)|_(αv)  (28)L _(β′) ∝|i _(βh)|_(αv)  (29)where | |α_(v) indicates averaging of an absolute value. Therefore,expression (21) is reduced to:

$\begin{matrix}{{\tan\;\left( {2\Delta\;\theta} \right)} = \frac{{i_{\alpha^{\prime}h}}_{\alpha\; v} - {i_{\beta^{\prime}h}}_{\alpha\; v}}{{i_{\alpha\; h}}_{\alpha\; v} - {i_{\beta\; h}}_{\alpha\; v}}} & (30)\end{matrix}$

As a result, the problem that a practical use is hardly attained in aconventional art can be solved by, in place of calculating instantaneousvalues of carrier currents, fetching only peak values and averagingthem.

Hereinafter, an embodiment of the invention will be described withreference to the drawings.

Referring to FIG. 2, a speed controller 1 compares a speed command valuewith a speed estimate value, and determines a q-axis current (torquecurrent) command iqRef so that the deviation in the comparison becomeszero. A q-axis current controller 2 compares iqRef with a current iqwhich is a current proportional to the torque among currents that areconverted to a coordinate system 10 (a d-q coordinate converter)rotating in synchronization with the rotor, and determines a voltagecommand Vq so that the deviation in the comparison becomes zero.

A d-axis current controller 4 compares idRef with a current id which isa current related to the magnetic pole direction among currents that areconverted to the coordinate system rotating in synchronization with therotor, and determines a voltage command Vd so that the deviation in thecomparison becomes zero. A noninterference controller 3 calculates speedelectromotive forces which interfere with each other between the d- andq-axes, and controls them so as to cancel influences on the currentcontrollers. A voltage amplitude and phase calculator 5 receives thevoltage commands Vd, Vq, and calculates the amplitude and phase of acommand voltage vector. A PWM controller 6 receives the amplitude andphase of the command voltage vector calculated by the voltage amplitudeand phase calculator 5, and generates an inverter switching signal. Thereference numeral 7 denotes an inverter main circuit which three-phasedrives an AC motor 8 by the switching signal. (The above is a vectorcontrolling portion for a usual AC motor.)

In FIG. 2, the portion constituting the apparatus for detecting amagnetic pole position of the invention includes: a circuit whichgenerates and outputs a high frequency for detecting a magnetic poleposition, on the basis of the carrier signal of the PWM controller 6; aportion which converts three-phase high-frequency currents by astationary coordinate converter 9 (an α-β coordinate converter), andthen converts to the rotating coordinate system (d-q) 10; and a portionwhich receives the three-phase high-frequency currents via a BPF 11,estimates θ by a pole position detector 12, performs detection of amagnetic pole position to use it as a control reference, and performsspeed estimation by a speed calculator 13.

Referring to FIG. 3, FIG. 3 is a detail view of the PWM controller 6which generates an arbitrary high frequency. A three-phase voltagecommand calculator 6-1 receives the amplitude and phase angle of thevoltage command vector which is calculated by the usual vectorcontrolling apparatus, and calculates voltage command values of threephases.

By contrast, in order to generate high frequencies which are differentfrom a driving frequency, in carrier signals having an arbitraryfrequency generated by a carrier signal generator 6-4, a phase shifter6-3 shifts the phase of the V-phase by an angle Δθ with respect to theU-phase, and shifts the W-phase by 2Δθ, and a comparator 6-2 comparesthe signals with the voltage command values and generates switchingsignals. The switching signals are input to the inverter main circuitdenoted by 7. (The detection of a magnetic pole position is performed byusing the high frequencies.)

Referring to FIG. 4, FIG. 4 is a diagram showing in detail theconfiguration of the pole position detector 12 shown in FIG. 2. Thethree-phase high-frequency currents from the BPF 11 shown in FIG. 2 areconverted by a coordinate converter 14 to the α-axis, the β-axis, theα′-axis, and the β′-axis, peak values of the converted currents arefetched, an averaging process is performed by an absolute valuecalculator 15 and a low-pass filter 16, and θ is estimated by a poleposition calculator 17.

Next, the operation will be described.

First, as shown in FIG. 3, in the carrier signals generated by thecarrier signal generator 6-4, the phase shifter 6-3 shifts the phase ofthe V-phase by an angle Δθ with respect to the U-phase, and shifts theW-phase by 2Δθ to output the high frequencies uuh, uvh, and uwh fordetecting a magnetic pole position such as shown in expression (1).

In the estimation of a magnetic pole position, first, the stationarycoordinate converter 9 extracts only an arbitrary frequency designatedin the band-pass filter 11, with respect to a detected voltage or acommand voltage and a detected current.

In the pole position detector 12 shown in FIG. 4, the three-phasehigh-frequency currents i output from the band-pass filter 11 areconverted by the coordinate converter 14 to the α-axis, the β-axis, theα′-axis, and the β′-axis. Then, the absolute value calculator 15implements a process of averaging peak values of the outputs (iα_(h),iβ_(h), iα′_(h), iβ′_(h)) of the coordinate converter 14. The low-passfilter 16 has an effect of more smoothing the outputs of the absolutevalue calculator 15. In the case where the number of samples of the peakvalues in the absolutizing process is large, the low-pass filter may beomitted. The outputs |iα_(h)|α_(v), |iβ_(h)|α_(v), |iα′_(h)|α_(v), and|iβ′_(h)|α_(v) of the low-pass filter 16 are proportional to theinductances of the axes as shown in expressions (26) to (29) above. Thesubsequent pole position calculator 17 calculates the magnetic poleposition from Δθ which is obtained by implementing the calculation ofexpression (30), and outputs the position. Therefore, a magnetic poleposition can be easily detected only from current values withoutcalculating inductances. Furthermore, it has been ascertained that, evenwhen the timing of current sampling is deviated by an addition of theaveraging process, an error due to the deviation scarcely occurs.

When the magnetic pole position is detected as described above, thespeed estimate value ω is estimated by the speed calculator 13, adeviation with respect to ωref is adjusted by the speed controller 1,and a q-axis current component iqref is output. The q-axis currentcontroller 2 outputs the voltage command Vq which is a result ofcomparison between iqref with the current iq that is obtained byconverting the three-phase high-frequency current to the α-β axes in thestationary coordinate converter 9, converting a result of the conversionwith respect to the d-axis by the d-q axis converter 10, and performinga vector control synchronized with the high-frequency currents. Thevalue of θ is adjusted. As a result, a motor control on the basis of thedetected magnetic pole position can be implemented.

While the invention has been described in detail with reference to aspecific embodiment, it will be understood by those skilled in the artthat various changes and modifications can be made without departingfrom the spirit and scope of the invention.

As described above, according to the invention, inductances on fourcoordinate axes can be calculated by using only carrier frequencycomponent currents which are converted to the coordinates, respectively,and calculations are conducted by using an average value obtained byfetching only peak values, in place of instantaneous values of thecarrier frequency component currents, thereby attaining an effect thatit is possible to easily solve the problem that a practical use ishardly attained in a conventional art because of complicatedsynchronization between the current detection timing and the positioncalculation.

1. A method of detecting a magnetic pole position of a motor havingelectric saliency, said method comprising: generating an arbitrary highfrequency in input voltages or input currents of the motor by means forproducing an arbitrary phase difference between a U-phase, a V-phase,and a W-phase, in said inverter, wherein said arbitrary high frequencyis not equal to an output frequency of a voltage source PWM inverter,converting said input voltages or said input currents to a firsttwo-phase stationary coordinate system in which a U-phase of threephases of said motor is α-axis and an axis intersecting said α-axis at90 deg. is β-axis, to generate first converted signals, detecting afirst current and a second current in respective said α- and β-axes,from the first converted signals, converting said input voltages or saidinput currents to a second two-phase stationary coordinate systemshifted by about 45 deg. from said first two-phase stationary coordinatesystem, axes of the second two-phase coordinate system being α′-axis andβ′-axis, to generate second converted signals, detecting a third currentand a fourth current in each of said α′- and β′-axes, from the secondconverted signals, and detecting a magnetic pole position of said motorby using said first, second, third, and fourth currents.
 2. The methodof detecting a magnetic pole position of a motor according to claim 1,wherein said magnetic pole position of said motor is detected by usingan output which is obtained by extracting peak currents from said first,second, third, and fourth currents that are detected respectively insaid four axes, and then passing said peak currents through a low-passfilter.
 3. An apparatus for detecting a magnetic pole position for amotor driven by a voltage source PWM inverter, said apparatuscomprising: means for producing an arbitrary phase difference in PWMcarrier signals between a U-phase, a V-phase, and a W-phase; means forgenerating and extracting only high-frequency currents; and means fordetecting a magnetic pole position by using said extracted highfrequency currents, wherein said means for detecting said magnetic poleposition detects said magnetic pole position by: generating an arbitraryhigh frequency in input voltages or input currents of the motor by themeans for producing the arbitrary phase difference between the U-phase,the V-phase, and the W-phase, wherein said arbitrary high frequency isnot equal to an output frequency of the voltage source PWM inverter,converting said input voltages or said input currents to a firsttwo-phase stationary coordinate system in which a U-phase of threephases of said motor is α-axis and an axis intersecting said α-axis at90 deg. is β-axis, to generate first converted signals, detecting afirst current and a second current in respective said α- and β-axes,from the first converted signals, converting said input voltages or saidinput currents to a second two-phase stationary coordinate systemshifted by about 45 deg. from said first two-phase stationary coordinatesystem, axes of the second two-phase coordinate system being α′-axis andβ′-axis, to generate second converted signals, detecting a third currentand a fourth current in each of said α′- and β′-axes, from the secondconverted signals, and detecting said magnetic pole position of saidmotor by using said first, second, third, and fourth currents.
 4. Anapparatus for detecting a magnetic pole position for a motor driven by avoltage source PWM inverter, said apparatus comprising: means forproducing an arbitrary phase difference in PWM carrier signals between aU-phase, a V-phase, and a W-phase; means for generating and extractingonly high-frequency currents; and means for detecting a magnetic poleposition by using said extracted high frequency currents, wherein saidmeans for detecting said magnetic pole position detects said magneticpole position by: generating an arbitrary high frequency in inputvoltages or input currents of the motor by means for producing thearbitrary phase difference between the U-phase, the V-phase, and theW-phase, wherein said arbitrary high frequency is not equal to an outputfrequency of the voltage source PWM inverter, converting said inputvoltages or said input currents to a first two-phase stationarycoordinate system in which a U-phase of three phases of said motor isα-axis and an axis intersecting said α-axis at 90 deg. is β-axis, togenerate first converted signals, detecting a first current and a secondcurrent in respective said α- and β-axes, from the first convertedsignals, converting said input voltages or said input currents to asecond two-phase stationary coordinate system shifted by about 45 deg.from said first two-phase stationary coordinate system, axes of thesecond two-phase coordinate system being α′-axis and β′-axis, togenerate second converted signals, detecting a third current and afourth current in each of said α′- and β′-axes, from the secondconverted signals, detecting said magnetic pole position of said motorby using said first, second, third, and fourth currents, and whereinsaid magnetic pole position of said motor is detected by using an outputwhich is obtained by extracting peak currents from said first, second,third, and fourth currents that are detected respectively in said fouraxes, and then passing said peak currents through a low-pass filter. 5.The method of detecting a magnetic pole position of a motor according toclaim 1, wherein said arbitrary phase difference is 120 deg., and saidarbitrary high frequency is an inverter carrier frequency.
 6. The methodof detecting a magnetic pole position of a motor according to claim 2,wherein said arbitrary phase difference is 120 deg., and said arbitraryhigh frequency is an inverter carrier frequency.
 7. The apparatus fordetecting a magnetic pole position for a motor according to any one ofclaim 3, wherein said arbitrary phase difference is 120 deg., and saidarbitrary high frequency is an inverter carrier frequency.
 8. Anapparatus for controlling a motor wherein said apparatus comprises acurrent controlling apparatus which splits a detected current into apole direction component and a torque component by using said positiondetected by an apparatus for detecting a magnetic pole position, whichfeedbacks said pole direction and said torque components to compare saidpole direction and said torque components with current a command valuefor said pole direction component and a current command value for saidtorque component in comparisons, and which implements a current controlso that deviations in said comparisons become zero, wherein theapparatus for detecting the magnetic pole position for the motor drivenby a voltage source PWM inverter comprises: means for producing anarbitrary phase difference in PWM carrier signals between a U-phase, aV-phase, and a W-phase; means for generating and extractinghigh-frequency currents from detected voltages or a command voltage anddetected currents; and means for detecting the magnetic pole position byusing said extracted high-frequency currents.
 9. An apparatus forcontrolling a motor wherein said apparatus comprises a speed detectingapparatus which detects a speed by using said position detected by theapparatus for detecting a magnetic pole position according to any one ofclaims 3 and
 8. 10. An apparatus for controlling a motor receiving saidposition detected by an apparatus for detecting a magnetic poleposition, wherein said apparatus for controlling the motor comprises: aspeed detecting apparatus which detects a speed by using said position;and a speed controlling apparatus which compares said speed detected bysaid speed detecting apparatus with a command speed, which implements aspeed control so that a deviation in said comparison becomes zero, andwhich outputs a torque command value or a current command valuecorresponding to a torque command, wherein the apparatus for detectingthe magnetic pole position for the motor driven by a voltage source PWMinverter comprises: means for producing an arbitrary phase difference inPWM carrier signals between a U-phase, a V-phase, and a W-phase; meansfor generating and extracting high-frequency currents from detectedvoltages or a command voltage and detected currents; and means fordetecting the magnetic pole position by using said extractedhigh-frequency currents.
 11. An apparatus for controlling a motorwherein said apparatus comprises a position controlling apparatus whichcompares said magnetic pole position detected on the basis of anapparatus for detecting a magnetic pole position, with a commandposition, which implements a position control so that a deviation insaid comparison becomes zero, and which outputs a speed command value,wherein the apparatus for detecting the magnetic pole position for themotor driven by a voltage source PWM inverter comprises: means forproducing an arbitrary phase difference in PWM carrier signals between aU-phase, a V-phase, and a W-phase; means for generating and extractinghigh-frequency currents from detected voltages or a command voltage anddetected currents; and means for detecting the magnetic pole position byusing said extracted high-frequency currents.
 12. An apparatus forcontrolling a motor wherein said apparatus comprises a torquecontrolling apparatus having the apparatus for detecting a magnetic poleposition for a motor driven by a voltage source PWM inverter, saidapparatus for detecting the magnetic pole position comprising: means forproducing an arbitrary phase difference in PWM carrier signals between aU-phase, a V-phase, and a W-phase; means for generating and extractingonly high-frequency currents; and means for detecting a magnetic poleposition by using said extracted high frequency currents, wherein saidarbitrary phase difference is 120 deg., and said arbitrary highfrequency is an inverter carrier frequency, said means for detectingsaid magnetic pole position detects said magnetic pole position by:generating an arbitrary high frequency in input voltages or inputcurrents of the motor by the means for producing the arbitrary phasedifference between the U-phase, the V-phase, and the W-phase, whereinsaid arbitrary high frequency is not equal to an output frequency of thevoltage source PWM inverter, converting said input voltages or saidinput currents to a first two-phase stationary coordinate system inwhich a U-phase of three phases of said motor is α-axis and an axisintersecting said α-axis at 90 deg. is β-axis, to generate firstconverted signals, detecting a first current and a second current inrespective said α- and β-axes, from the first converted signals,converting said input voltages or said input currents to a secondtwo-phase stationary coordinate system shifted by about 45 deg. fromsaid first two-phase stationary coordinate system, axes of the secondtwo-phase coordinate system being α′-axis and β′-axis, to generatesecond converted signals, detecting a third current and a fourth currentin each of said α′- and β′-axes, from the second converted signals, anddetecting said magnetic pole position of said motor by using said first,second, third, and fourth currents.
 13. An apparatus for controlling amotor wherein said apparatus comprises a speed controlling apparatushaving the apparatus for detecting a magnetic pole position for a motordriven by a voltage source PWM inventor, said apparatus for detectingthe magnetic pole position comprising: means for producing an arbitraryphase difference in PWM carrier signals between a U-phase, a V-phase,and a W-phase; means for generating and extracting only high-frequencycurrents; and means for detecting a magnetic pole position by using saidextracted high frequency currents, wherein said arbitrary phasedifference is 120 deg., and said arbitrary high frequency is an invertercarrier frequency, said means for detecting said magnetic pole positiondetects said magnetic pole position by: generating an arbitrary highfrequency in input voltages or input currents of the motor by the meansfor producing the arbitrary phase difference between the U-phase, theV-phase, and the W-phase, wherein said arbitrary high frequency is notequal to an output frequency of the voltage source PWM inverter,converting said input voltages or said input currents to a firsttwo-phase stationary coordinate system in which a U-phase of threephases of said motor is α-axis and an axis intersecting said α-axis at90 deg. is β-axis, to generate first converted signals, detecting afirst current and a second current in respective said α- and β-axes,from the first converted signals, converting said input voltages or saidinput currents to a second two-phase stationary coordinate systemshifted by about 45 deg. from said first two-phase stationary coordinatesystem, axes of the second two-phase coordinate system being α′-axis andβ′-axis, to generate second converted signals, detecting a third currentand a fourth current in each of said α′- and β′-axes, from the secondconverted signals, and detecting said magnetic pole position of saidmotor by using said first, second, third, and fourth currents.
 14. Anapparatus for controlling a motor wherein said apparatus comprisesposition controlling apparatus having the apparatus for detecting amagnetic pole position for a motor driven by a voltage source PWMinverter, said apparatus for detecting the magnetic pole positioncomprising: means for producing an arbitrary phase difference in PWMcarrier signals between a U-phase, a V-phase, and a W-phase; means forgenerating and extracting only high-frequency currents; and means fordetecting a magnetic pole position by using said extracted highfrequency currents, wherein said arbitrary phase difference is 120 deg.,and said arbitrary high frequency is an inverter carrier frequency, saidmeans for detecting said magnetic pole position detects said magneticpole position by: generating an arbitrary high frequency in inputvoltages or input currents of the motor by the means for producing thearbitrary phase difference between the U-phase, the V-phase, and theW-phase, wherein said arbitrary high frequency is not equal to an outputfrequency of the voltage source PWM inverter, converting said inputvoltages or said input currents to a first two-phase stationarycoordinate system in which a U-phase of three phases of said motor isα-axis and an axis intersecting said α-axis at 90 deg. is β-axis, togenerate first converted signals, detecting a first current and a secondcurrent in respective said α- and β-axes, from the first convertedsignals, converting said input voltages or said input currents to asecond two-phase stationary coordinate system shifted by about 45 deg.from said first two-phase stationary coordinate system, axes of thesecond two-phase coordinate system being α′-axis and β′-axes, togenerate second converted signals, detecting a third current and afourth current in each of said α′- and β′-axes, from the secondconverted signals, and detecting said magnetic pole position of saidmotor by using said first, second, third, and fourth currents.
 15. Anapparatus for controlling a motor wherein said apparatus comprises aspeed detecting apparatus which detects a speed by using said positiondetected by the apparatus for detecting a magnetic pole position for amotor driven by a voltage source PWM inverter, said apparatuscomprising: means for producing an arbitrary phase difference in PWMcarrier signals between a U-phase, a V-phase, and a W-phase; means forgenerating and extracting high-frequency currents from detected voltagesor a command voltage and detected currents; means for detecting amagnetic pole position by using said extracted high-frequency currents;and a speed controlling apparatus comparing said speed detected by saidspeed detecting apparatus with a command speed in a comparison, saidspeed controlling apparatus implementing a speed control so that adeviation in said comparison becomes zero, and outputting a torquecommand value or a current command value corresponding to a torquecommand.
 16. An apparatus for controlling a motor wherein said apparatuscomprises a current controlling apparatus which splits a detectedcurrent into a pole direction component and a torque component by usingsaid position detected by an apparatus for detecting a magnetic poleposition, which feedbacks said pole direction and said torque componentsto compare said pole direction and said torque components with current acommand value for said pole direction component and a current commandvalue for said torque component in comparisons, and which implements acurrent control so that deviations in said comparisons become zero,wherein the apparatus for detecting the magnetic pole position for themotor driven by a voltage source PWM inverter comprises: means forproducing an arbitrary phase difference in PWM carrier signals between aU-phase, a V-phase, and a W-phase; means for generating and extractingonly high-frequency currents; and means for detecting a magnetic poleposition by using said extracted high-frequency currents.
 17. Anapparatus for controlling a motor receiving said position detected by anapparatus for detecting a magnetic pole position, wherein said apparatusfor controlling the motor comprises: a speed detecting apparatus whichdetects a speed by using said position; and a speed controllingapparatus which compares said speed detected by said speed detectingapparatus with a command speed, which implements a speed control so thata deviation in said comparison becomes zero, and which outputs a torquecommand value or a current command value corresponding to a torquecommand, wherein the apparatus for detecting the magnetic pole positionfor the motor driven by a voltage source PWM inverter comprises: meansfor producing an arbitrary phase difference in PWM carrier signalsbetween a U-phase, a V-phase, and a W-phase; means for generating andextracting only high-frequency currents; and means for detecting amagnetic pole position by using said extracted high-frequency currents.18. An apparatus for controlling a motor wherein said apparatuscomprises a position controlling apparatus which compares said magneticpole position detected on the basis of an apparatus for detecting amagnetic pole position, with a command position, which implements aposition control so that a deviation in said comparison becomes zero,and which outputs a speed command value, wherein the apparatus fordetecting the magnetic pole position for the motor driven by a voltagesource PWM inverter comprises: means for producing an arbitrary phasedifference in PWM carrier signals between a U-phase, a V-phase, and aW-phase; means for generating and extracting only high-frequencycurrents; and means for detecting a magnetic pole position by using saidextracted high-frequency currents.
 19. An apparatus for controlling amotor wherein said apparatus comprises a speed detecting apparatus whichdetects a speed by using said position detected by the apparatus fordetecting a magnetic pole position for a motor driven by a voltagesource PWM inverter, said apparatus comprising: means for producing anarbitrary phase difference in PWM carrier signals between a U-phase, aV-phase, and a W-phase; means for generating and extracting onlyhigh-frequency currents; means for detecting a magnetic pole position byusing said extracted high-frequency currents, and a speed controllingapparatus comparing said speed detected by said speed detectingapparatus with a command speed in a comparison, said speed controllingapparatus implementing a speed control so that a deviation in saidcomparison becomes zero, and outputting a torque command valve or acurrent command value corresponding to a torque command.